Wood fibre based panel with a surface layer

ABSTRACT

A building panel with a surface layer (1) including a wood veneer, a wood fibre based core (2) and a sub-layer (3) between the surface layer (1) and the core (2). The sub-layer (3) includes wood fibres (4) and a binder (5). The surface layer (1) has surface portions (6) including material from the sub-layer (3). The surface portions (6) including material from the sub-layer (3) extend into the wood veneer.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of Swedish Application No.1450023-5, filed on Jan. 10, 2014, the benefit of Swedish ApplicationNo. 1450552-3, filed on May 12, 2014, and the benefit of SwedishApplication No. 1451154-7, filed on Sep. 29, 2014. The entire contentsof each of Swedish Application No. 1450023-5, Swedish Application No.1450552-3, and Swedish Application No. 1451154-7 are hereby incorporatedherein by reference in their entirety.

TECHNICAL FIELD

The disclosure generally relates but is not limited to the field of woodfibre based building panels with a surface layer, preferably floorpanels, wall panels and furniture components.

TECHNICAL BACKGROUND

Embodiments of the disclosure are particularly suitable for use infloating floors, which are formed of floor panels with a wood fibre coreand a decorative wear resistant surface. The following description ofknown technique, problems of known systems and objects and features ofthe disclosure will therefore, as a non-restrictive example, be aimedabove all at this field of application and in particular at flooringswhich are similar to traditional wood fibre based laminate floorings.

It should be emphasized that the embodiments of the disclosure can alsobe used in other applications as, for example, wall panels, ceilings,furniture components, and similar.

KNOWN TECHNIQUE AND PROBLEMS THEREOF

Several technologies are used to provide a floor panel, which is a copyof a solid floor panel. The reason is that copies may be produced morecost efficient and a floor with a separate layer attached to a core offor example HDF or plywood is more moisture stable than solid woodfloors.

Wood fibre based direct pressed laminated flooring usually comprises acore of a 6-12 mm fibre board, a 0.2 mm thick upper decorative surfacelayer of laminate and a 0.1-0.2 mm thick lower balancing layer oflaminate, plastic, paper or like material.

A laminate surface generally comprise two paper sheets, a 0.1 mm thickprinted decorative paper and a transparent 0.05-0.1 mm thick overlayintended to protect the decorative paper from abrasion. The transparentoverlay, which is made of

-cellulose fibres, comprises small hard and transparent aluminium oxideparticles, which gives the surface layer a high wear resistance.

The printed decorative paper and the overlay are impregnated withmelamine resin and laminated to a wood fibre based core under heat andpressure. The two papers have prior to pressing a total thickness ofabout 0.3 mm and they are after pressing compressed to about 0.2 mm.

Other common surface materials are wood veneer and foils, which areglued to a core. The surface may also be a powder layer comprising woodfibres, melamine resins, colour pigments and aluminium oxide particles.

Wood veneers may provide the most natural copies. The disadvantage isthat a wood veneer generally has a lower impact resistance than laminatefloors and the production cost is high when high quality veneers may beused

It is known that a wood veneer may be pressed on a powder layer asdescribed above and that such a powder layer may provide increasedimpact resistance. This will not solve the cost problems.

U.S. Pat. No. 2,831,793 discloses a composite wood veneer panel. A thinveneer is applied to a composite fibrous core of ligno-celluloseparticles and binder and openings of the veneer are filled with corematerial when pressed together to form the composite panel. In themanufacture of the plywood or veneered panels according to thisdocument, the plugging of the surface layer opening defects is donesimultaneously with the formation of the board.

SUMMARY

The objective of at least certain embodiments of the disclosure is toprovide a building panel, such as a floor panel, with a wood basedsurface layer, which has a more attractive surface design and/or bettersurface properties and/or cost structure than present known floorings.

At least some of these and other objects and advantages that will beapparent from the description have been achieved by a building panelcomprising a surface layer comprising a wood veneer, a wood fibre basedcore, and a sub-layer arranged between the surface layer and the woodfibre based core. The sub-layer comprises wood fibres and a binder. Thesurface layer has surface portions comprising material from thesub-layer extending into the wood veneer.

By extending into the wood veneer is meant that the material from thesub-layer extends, for example, at least into ⅓ of the thickness of thewood veneer. In one embodiment, the material of the sub-layer extendscompletely through the wood veneer.

The surface portions comprising material from the sub-layer may be flushwith a remainder of the surface layer.

In an embodiment, the core may be a wood-based board, for example, awood-fibre based board such as MDF or HDF, or plywood. The core may be aWood Plastic Composite (WPC). In an embodiment, the core may be amineral composite board, a fibre cement board, a magnesium oxide cementboard, a ceramic board, or a plastic board such as a thermoplasticboard.

Preferably, the core is a pre-fabricated core.

In an embodiment, the veneer layer may be a wood veneer, a cork veneer,or a stone veneer.

In an embodiment, the sub-layer may comprise a filler and a binder. Thefillers may be particles or fibres, for example wood fibres orparticles, or mineral particles or fibres. The wood particles may belignocellulosic particles and/or cellulosic particles. The woodparticles may be at least partially bleached. The fillers may be rice,straw, corn, jute, linen, flax, cotton, hemp, bamboo, bagasse or sisalparticles or fibres. The filler may be starch such as maize starch,potato starch, etc.

The thickness of the veneer may be in the range of about 0.2 mm to about1 mm.

The building panel may be provided with a thinner veneer than knownbuilding panels with veneer, since the sub-layer reinforces the veneer.

The building panel may be provided with a partly broken veneer thatcomprises holes, such as cracks, through the veneer. The sub-layer mayprotrude through the holes and level the surface layer. The sub-layermay be used as an alternative for putty for a building panel with abroken surface layer. Material from the sub-layer may fill holes, suchas cracks, of the veneer.

The veneer may also be pre-treated prior to pressing, for example, bebrushed.

The surface layer may comprise embossed portions and a part of thesub-layer may be more compressed under an embossed portion than under anon-embossed surface portion.

The embossed portions may be naturally occurring after pressing. Forwood veneers having a porous structure, such as hard wood (e.g.,angiosperm), porous portions of the veneer form embossed portions afterpressing, since these portions do not spring back from their compressedstate when the pressure is released. These porous portions are filledwith the binder of the sub-layer during pressing. Then the binder curesand/or hardens, the binder locks the position of the porous portions inthe compressed state.

The portions of veneer having high density, i.e. being non-porous, arecompressed during pressing but spring back when the pressure isreleased, thus forming protrusions of the surface layer. Thehigh-density portions do not absorb enough binder from the sub-layer tobe locked by the hardened binder after pressing.

For wood veneer having a non-porous structure, such as soft wood (e.g.,gymnosperm), the summer wood annual rings (also called late wood annualrings), having high density, are not compressible during pressing.Instead, the summer wood annual rings are pressed into the sub-layersuch that the sub-layer is compressed. The summer wood annual rings formembossed portions of the surface layer. The spring wood annual rings(also called early wood annual rings) are compressible during pressing.During pressing, the spring wood annual rings are compressed. Then thepressure is released, the spring wood annual rings spring back, and formprotrusions.

The embossed portions of the surface layer may also be formed bypressing by an embossed pressing device, such as an embossed pressplate.

The building panel may comprise a powder based balancing layer. Thepowder based balancing layer may comprise cellulose or lignocellulosicparticles and a binder. In one embodiment, the building panel comprisesa balancing layer comprising a resin impregnated paper, preferablyimpregnated with a thermosetting binder.

The building panel may be a floor panel comprising a powder basedbalancing layer. The powder based balancing layer may comprise celluloseor lignocellulosic particles and a binder. In one embodiment, the floorpanel comprises a balancing layer comprising a resin impregnated paper,preferably impregnated with a thermosetting binder.

The binder in the sub-layer may be a thermosetting resin.

The binder in the sub-layer may be a melamine resin. The binder in thesub-layer may be an amino resin, such as melamine formaldehyde resin,urea formaldehyde resin, phenol formaldehyde resin, or a combinationthereof.

The binder in the sub-layer may be a thermoplastic binder. Thethermoplastic binder may be polyvinyl chloride (PVC), polyethylene (PE),polypropylene (PP), polyurethane (PU), polyvinyl alcohol (PVOH),polyvinyl butyral (PVB), and/or polyvinyl acetate (PVAc), or acombination thereof.

The binder may be wood mastic, wood filler or any other type ofputty-like paste.

The sub-layer may be substantially or completely formaldehyde free.

The wood fibres in the sub-layer may be lignocellulosic and/orcellulosic particles. The wood fibres may be at least partiallybleached.

The sub-layer may comprise wear resistant particles.

The sub-layer may further comprise colour pigments and/or a colorant.The colour pigment may be of dark colour, or may be white, such as TiO2.

The wood veneer may comprise holes and/or cracks, wherein the sub-layerfills the holes and/or cracks of the wood veneer.

The surface layer may further comprise a protective overlay, comprisingwear resistant particles, arranged on the wood veneer.

The sub-layer may comprise a foaming agent. Additives such as blowingagents may be included in the sub-layer. The blowing agents may bephysical foaming agents such as Expancel® and/or chemical blowing agentssuch as AlBN (azoisobutyronitrile) or ADC (azodicarbonamide).

The surface layer may be a cork layer.

The building panel may be a floor panel, a wall panel, a ceiling panel,a furniture component, skirting boards, mouldings, edging profiles etc.

An alternative to the veneer may be a paper or a plastic foil providedwith apertures that extends through the paper or the plastic foil.

A second aspect of the disclosure is a method to produce a buildingpanel, comprising the step of:

-   -   applying a wood fibre powder and a binder on a wood fibre based        core, to obtain a sub-layer;    -   applying a wood veneer, comprising holes through the veneer, on        the sub-layer,    -   applying heat and pressure to bond the veneer, the sub-layer and        the wood fibre based core together, wherein a portion of the        wood fibre powder and the binder is pressed into the holes.

The method preferably comprises the step of applying a foaming agent.The foaming agent may facilitate the displacement of the wood fibrepowder and the agent into the holes.

The wood fibre powder may comprise lignocellulosic particles orcellulose particles.

The method may comprise the step of applying different colour pigments,such that the colour of the visible sub-layer portion varies along thebuilding panel, or such that the portion of the sub-layer in the holesforms a pattern.

After applying pressure, the surface layer may comprise embossedportions, and wherein a part of the sub-layer is more compressed underan embossed surface portion than under a non-embossed surface portion.

The method may further comprise applying a protective overlay with wearresistant particles on the wood veneer, preferably prior to pressing.

The sub-layer may further comprise colour pigments and/or a colorant.

The sub-layer may comprise wear resistant particles.

According to a third aspect of the disclosure, a building panel isprovided. The building panel comprises a surface layer comprising a woodveneer, a core, and a sub-layer arranged between the surface layer andthe core. The surface layer has surface portions comprising materialfrom the sub-layer extending into the wood veneer.

Preferably, the core is a wood fibre based core.

Preferably, the sub-layer comprises wood fibres and a binder.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will by way of example be described in more detail withreference to the appended schematic drawing, which shows an embodimentof the disclosure.

FIG. 1 illustrates a building panel according to an embodiment of thedisclosure.

DETAILED DESCRIPTION

FIG. 1 shows a building panel with a surface layer 1 comprising a woodveneer, a core 2, and a sub-layer 3 arranged between the surface layer 1and the core 2. The core 2 may be wood fibre based board such as MDF,HDF, particle board, plywood, OSB etc. The core 2 may be a WPC (WoodPlastic Composite). The core 2 may in one embodiment be a mineral board.The building panel may be a floor panel, a wall panel, a ceiling panel,a furniture component, skirting boards, mouldings, edging profiles, etc.

A low quality wood veneer is used as a surface layer 1. The veneercomprises cracks and other similar defects. The veneer is pressedagainst the core 2 with a powder based sub-layer 3 comprising woodfibres 4 and a binder 5 such that the powder floats and fills thecracks. The panel comprises after pressing a surface layer 1 withsurface portions 6 comprising material from the sub-layer 3. The surfaceportions 6 comprising material from the sub-layer 3 extend into the woodveneer. The surface portions comprising material from the sub-layer maybe flush with a remainder of the surface layer. A “surface portion” is aportion of the surface layer that is visible on the exposed surface ofthe surface layer facing away from the core.

In one embodiment, the sub-layer 3 comprises a binder applied in liquidform.

The panel may be pressed against an embossed press plate such that apart of the sub-layer 3 is more compressed under an embossed portion 8than under a non-embossed surface portion.

Preferably the building panel is a floor panel that may have a powderbased balancing layer 7. A powder based balancing layer 7 may also beapplied on any other type of building panel. The powder based balancinglayer 7 may comprise lignocellulosic particles or cellulose particlesand a binder, preferably a thermosetting binder, more preferably anamino resin such as melamine formaldehyde resin. The binder may also beapplied in powder form, the sub-layer 3 being a dry powder layer. In oneembodiment, the sub-layer 3 is a pre-pressed layer, wherein the binderhas not completely cured during the pre-pressing.

The binder of the sub-layer 3 may be a thermosetting resin, such as,for, example a melamine formaldehyde resin. The sub-layer 3 may alsocomprise colour pigments and wear resistant particles such as aluminiumoxide particles. The wood fibres of the sub-layer 3 may belignocellulosic particles or cellulose particles. The wood fibres of thesub-layer 3 may be at least partially bleached. The sub-layer maycomprise a foaming agent. The wood veneer may be replaced by a corkveneer or a stone veneer.

The sub-layer 3 may be applied in an amount of 200-600 g/m2, preferably300-500 g/m2 such as about 400 g/m2. The amount of binder applied forthe sub-layer 3 may be 100-300 g/m2, preferably 150-250 g/m2 such asabout 200 g/m2. The sub-layer 3 may comprise the binder in an amount of30-80 wt %, preferably in an amount of 40-60 wt % such as about 50 wt %.

In an embodiment, a produced building panel may be 6-25 mm thick,preferably 8-15 mm thick after pressing, while the core may be 5-22 mmthick, preferably 7-14 mm thick. The sub-layer may be 0.1-2 mm thickafter pressing.

Using a protective overlay with wear resistant particles applied on theveneer is not excluded and this could increase the wear resistance of awood veneer. Dry and wet overlays, which are produced by productionmethods where for example thermosetting resins in dry or wet form aremixed with aluminium oxide, without any fibres could also be used.Aluminium oxide particles mixed with melamine powder could for examplebe applied on a wood veneer prior to pressing and a wear resistantsurface could be obtained without any surface coating after pressing.Dry and wet overlays may be applied on the surface layer prior topressing. Wax may be applied, for example, as a powder, prior topressing on the veneer. A lacquer may also be applied on the surfacelayer after pressing. A protective foil may also be applied on theveneer prior to pressing or on the surface layer after pressing.

It is also contemplated that the building panel is provided with asecond surface layer (not shown) comprising a wood veneer of the abovedescribed type. A sub-layer of the above described type is arrangedbetween the second surface layer and a second surface of the core of theabove described type. The second surface layer has surface portionscomprising material from the sub-layer extending into the wood veneer.The second surface of the core faces away from the surface layerdescribed above with reference to FIG. 1. In this embodiment, thesurface layer described above with reference to FIG. 1 is considered asfirst surface layer.

The building panel may be produced by a method comprising the step of:

-   -   applying a wood fibre powder and a binder on a wood fibre based        core, to obtain a sub-layer;    -   applying a wood veneer, comprising holes through the veneer, on        the sub-layer,    -   applying heat and pressure to bond the veneer, the sub-layer and        the wood fibre based core together, wherein a portion of the        wood fibre powder and the binder is pressed into the holes.

The method preferably comprises the step of applying a foaming agent.The foaming agent may facilitate the displacement of the wood fibrepowder and the agent into the holes.

The wood fibre powder may comprise lignocellulosic particles orcellulose particles.

The method may comprise the step of applying different colour pigments,such that the colour of the visible sub-layer portion varies along thebuilding panel, or such that the portion of the sub-layer in the holesforms a pattern.

The invention claimed is:
 1. A building panel comprising: a surfacelayer comprising a wood veneer, the wood veneer comprising porousportions and non-porous portions, a wood fibre based core, and asub-layer arranged between the surface layer and the wood fibre basedcore, the sub-layer being a separate discrete layer from the core,wherein the sub-layer comprises wood fibres and a binder, wherein thesurface layer has surface portions comprising material from thesub-layer extending into the wood veneer, and wherein the surface layercomprising embossed portions and protrusions, wherein the binder of thesub-layer bonds the porous portions of the wood veneer in a compressedposition to form the embossed portions, and wherein the binder does notbond the non-porous portions of the wood veneer in the compressedposition so that the non-porous portions of the wood veneer form theprotrusions.
 2. The building panel as claimed in claim 1, wherein thesurface portions comprising material from the sub-layer are flush withat least a portion of the surface layer.
 3. The building panel asclaimed in claim 1, wherein the sub-layer comprises colour pigmentsand/or a colorant.
 4. The building panel as claimed in claim 1, whereinthe sub-layer comprises wear resistant particles.
 5. The building panelas claimed in claim 1, further comprising a powder-based balancinglayer.
 6. The building panel as claimed in claim 1, wherein the woodveneer comprises holes and/or cracks, wherein the sub-layer fills theholes and/or cracks of the wood veneer.
 7. The building panel as claimedin claim 1, further comprising a protective overlay comprising wearresistant particles arranged on the surface layer.
 8. The building panelas claimed in claim 1, wherein the binder is liquid.
 9. The buildingpanel as claimed in claim 1, wherein the binder in the sub-layer is athermosetting resin.
 10. The building panel as claimed in claim 1,wherein the binder in the sub-layer is a melamine formaldehyde resin.11. The building panel as claimed in claim 1, wherein the sub-layercomprises a foaming agent.
 12. The building panel as claimed in claim11, wherein the foaming agent includes a chemical blowing agentadditive.
 13. The building panel as claimed in claim 1, furthercomprising: a second surface layer comprising a second wood veneer, thesecond surface layer being arranged on an opposite side of the core fromthe surface layer; and a second sub-layer arranged between the secondsurface layer and the core, wherein the second surface layer has surfaceportions comprising material from the second sub-layer extending intothe second wood veneer.
 14. A building panel comprising: a surface layercomprising a wood veneer, the wood veneer comprising porous portions andnon-porous portions, a wood fibre based core, and a sub-layer arrangedbetween the surface layer and the wood fibre based core, wherein thesub-layer comprises wood fibres, a binder and colour pigments and/or acolorant, wherein the surface layer has surface portions comprisingmaterial from the sub-layer extending into the wood veneer, and whereinthe surface layer comprising embossed portions and protrusions, whereinthe binder of the sub-layer bonds the porous portions of the wood veneerin a compressed position to form the embossed portions, and wherein thenon-porous portions of the wood veneer form the protrusions bycontaining less of the binder than the porous portions.
 15. The buildingpanel as claimed in claim 14, further comprising a powder-basedbalancing layer.
 16. The building panel as claimed in claim 15, furthercomprising a protective overlay comprising wear resistant particlesarranged on the surface layer.
 17. A building panel comprising: asurface layer comprising a wood veneer, the wood veneer comprisingporous portions and non-porous portions, a wood fibre based core, and asub-layer arranged between the surface layer and the wood fibre basedcore, wherein the sub-layer comprises wood fibres, a binder and wearresistant particles, wherein the surface layer has surface portionscomprising material from the sub-layer extending into the wood veneer,wherein the binder is between 40-60 wt-% of the sub-layer, and whereinthe surface layer comprising embossed portions and protrusions, whereinthe binder of the sub-layer bonds the porous portions of the wood veneerin a compressed position to form the embossed portions, and wherein thebinder does not bond the non-porous portions of the wood veneer in thecompressed position so that the non-porous portions of the wood veneerform the protrusions.
 18. The building panel as claimed in claim 17,wherein the binder is liquid.
 19. The building panel as claimed in claim17, wherein the sub-layer comprises a foaming agent.
 20. The buildingpanel as claimed in claim 17, further comprising a powder-basedbalancing layer.
 21. The building panel as claimed in claim 20, furthercomprising a protective overlay comprising wear resistant particlesarranged on the surface layer.
 22. A building panel comprising: asurface layer comprising a wood veneer, the wood veneer comprisingrelatively high-density portions and relatively low-density portions, awood fibre based core, and a sub-layer arranged between the surfacelayer and the wood fibre based core, the sub-layer being a separatediscrete layer from the core, wherein the sub-layer comprises woodfibres and a binder, wherein the surface layer has surface portionscomprising material from the sub-layer extending into the wood veneer,and wherein the surface layer comprises embossed portions andprotrusions, wherein the binder of the sub-layer bonds the relativelylow-density portions of the wood veneer in a compressed position to formthe embossed portions, and wherein the binder does not bond therelatively high-density portions of the wood veneer in the compressedposition so that the relatively high-density portions of the wood veneerform the protrusions.